Hematophagous arthropod infestation of animals is a health and economic concern because hematophagous arthropods are known to cause and/or transmit a variety of diseases. Hematophagous arthropods directly cause a variety of diseases, including allergies, and also carry a variety of infectious agents including, but not limited to, endoparasites (e.g., nematodes, cestodes, trematodes and protozoa), bacteria and viruses. In particular, the bites of hematophagous arthropods are a problem for animals maintained as pets because the infestation becomes a source of annoyance not only for the pet but also for the pet owner who may find his or her home generally contaminated with insects. As such, hematophagous arthropods are a problem not only when they are on an animal but also when they are in the general environment of the animal.
Bites from hematophagous arthropods are a particular problem because they not only can lead to disease transmission but also can cause a hypersensitive response in animals which is manifested as disease. For example, bites from fleas can cause an allergic disease called flea allergic (or allergy) dermatitis (FAD). A hypersensitive response in animals typically results in localized tissue inflammation and damage, causing substantial discomfort to the animal.
The medical importance of arthropod infestation has prompted the development of reagents capable of controlling arthropod infestation. Commonly encountered methods to control arthropod infestation are generally focused on use of insecticides. While some of these products are efficacious, most, at best, offer protection of a very limited duration. Furthermore, many of the methods are often not successful in reducing arthropod populations. In particular, insecticides have been used to prevent hematophagous arthropod infestation of animals by adding such insecticides to shampoos, powders, collars, sprays, foggers and liquid bath treatments (i.e., dips). Reduction of hematophagous arthropod infestation on the pet has been unsuccessful for one or more of the following reasons: (1) failure of owner compliance (frequent administration is required); (2) behavioral or physiological intolerance of the pet to the pesticide product or means of administration; and (3) the emergence of hematophagous arthropod populations resistant to the prescribed dose of pesticide. Hematophagous arthropod populations, however, have been found to become resistant to insecticides.
Juvenile hormone (JH) regulates growth and development of immature insects, and is involved in reproductive processes in adult insects. JH levels are controlled by two degradative enzymes, juvenile hormone esterase and juvenile hormone epoxide hydrolase.
Prior investigators have described insect juvenile hormone epoxide hydrolase (JHEH) protein biochemistry, for example, Touhara et al., J. Biol. Chem., 268: 19604-19609, 1993 and Khlebodarova et al., Insect Biochem. Molec Biol, 26: 829-835, 1996. Prior investigators have described certain insect epoxide hydrolase (EH) nucleic acid and amino acid sequences, for example, Wojtasek et al., Biochem. Biophys. Res. Comm., 220: 323-329, 1996 describes Manduca sexta JHEH sequences and Roe et al., Arch. Insect Biochem. Physiol., 32: 527-535, 1996. Mammalian EH genes have been cloned, none of which have more than 40% identity with the nucleic acid molecules of the present invention.
Identification of an EH of the present invention is unexpected, however, because even the most similar nucleic acid sequence identified by previous investigators could not be used to identify an EH of the present invention. In addition, identification of an EH protein of the present invention is unexpected because the inventors of the present invention identified highly conserved regions of epoxide hydrolase sequences suitable for the production of degenerate primers. Production of primers to such conserved regions is not taught or suggested by previous investigators.
In summary, there remains a need to develop a reagent and a method to protect animals from hematophagous arthropod infestation.